Editing Mulesing (section)

===Breeding programs===
Merino sheep bred on selection principles may be more resistant to flystrike because they are plain bodied (lower skin wrinkling around the breech). Studies have shown that flystrike is lower in plain bodied sheep. However, mulesed animals had consistently lower flystrike than unmulesed regardless of body type.<ref>{{Cite book
 | first1 = J. L.
 | last1 = Smith
 | first2 = H. G.
 | last2 = Brewer
 | first3 = T.
 | last3 = Dyall
 | title= HERITABILITY AND PHENOTYPIC CORRELATIONS FOR BREECH STRIKE AND BREECH STRIKE RESISTANCE INDICATORS IN MERINOS
 | series = 18
 | pages = 334–337
 | publisher = Association Advancement of Animal Breed Genetics
 | url = http://www.aaabg.org/proceedings18/files/smith334.pdf
 }}</ref>

The resistance of plain-bodied Merino sheep to flystrike arose from field investigations by Australian scientists, Drs H. R. Seddon and H. B. Belschner, in the early 1930s. Non-mulesed Merino ewe bodies were graded as plain (A class), wrinkly (B class) and very wrinkly (C class). The plain-bodied (A class) Merino ewes were much less susceptible to flystrike than wrinkly-bodied Merinos (B and C class).

In these Merino flocks, the sheep are plainer than the plain-bodied (A class) Merino ewes and therefore more resistant to flystrike. The rams and semen from these studs are used in over 3,000 of the 45,000 Merino farms in Australia. Using breeding principles, wrinkle-skinned Merino flocks which require mulesing have been transformed into plain-bodied and mules-free flocks within five years.<ref name="ABC-2007-04">{{cite web|author=de Landgrafft|first=Tara|date=24 April 2007|title=New Zealand farmers on the ball with bare breech breeding|url=http://www.abc.net.au/rural/wa/content/2006/s1905645.htm|url-status=dead|access-date=2007-05-01|work=ABC Rural News|publisher=Australian Broadcasting Corporation|archive-date=16 March 2008|archive-url=https://web.archive.org/web/20080316111504/http://www.abc.net.au/rural/wa/content/2006/s1905645.htm}}</ref><ref>Watts, J: "The Genetic Alternative to Mulesing Plain-Bodied Sheep", ''Australian Farm Journal'', p. 43–45, May 2008.</ref><ref>Watts, J: "Fly Strike Resistance. Non-Mulesed Merinos", ''Australian Farm Journal'', p. 52–55, July 2008.</ref><ref>Watts, J: "Breeding Mules-Free Merinos Within Five Years", ''Australian Farm Journal'', p. 45–47, October 2008.</ref><ref name="AWI Alternatives"/>